Semiconductor image sensors are used for sensing light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital still camera or mobile phone camera applications. These devices utilize an array of pixels in a substrate, including photodiodes and transistors that can absorb radiation projected toward the substrate and convert the sensed radiation into electrical signals.
A backside illuminated (BSI) image sensor device is one type of image sensor device. As the size of transistor devices shrink with each technology generation, existing BSI image sensor devices may begin to suffer from issues related to cross-talk and blooming. These issues may be caused by insufficient isolation between neighboring pixels of the BSI image sensor. Therefore, while existing methods of fabricating BSI image sensor devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.